bimbeano
11742
You need a third one !
Audi RS6 Avant 
In your case the M3 is my preference, although it is waaaaaaay too fast .. at least where I live.
But for the German autobahn these cars are simply perfect.
So in a perfect world where I live in Germany my choice would be a BMW 340d with some upgrades to get the power up to 400+ hp. Topspeed of around 280 kph is more than enough and fuel consumption would be acceptable ;-)
Bim